EXIT COSTS AND RESTRUCTURING RESERVES - Narrative (Details) - USD ($)	3 Months Ended	12 Months Ended
	Mar. 31, 2016	Dec. 31, 2015
Restructuring Cost and Reserve [Line Items]
Restructuring charges incurred	$ 0	$ 26,000,000
Outside Services
Restructuring Cost and Reserve [Line Items]
Restructuring charges incurred		8,000,000
Salaries & Employee Benefits | Salaries & Employee Benefits
Restructuring Cost and Reserve [Line Items]
Restructuring charges incurred		1,000,000
Occupancy & Equipment | Occupancy & Equipment
Restructuring Cost and Reserve [Line Items]
Restructuring charges incurred		$ 17,000,000